A novel proxy to examine interspecific phosphorus facilitation between plant species

Resource complementarity can contribute to enhanced ecosystem functioning in diverse plant communities, but the role of facilitation in the enhanced complementarity is poorly understood. Here, we use leaf manganese concentration ([Mn]) as a proxy for rhizosheath carboxylate concentration to explore novel mechanisms of complementarity mediated by phosphorus (P) facilitation. In pot experiments, we showed that mixtures involving Carex korshinskyi, an efficient P-mobilizing species, exhibited greater biomass and relative complementarity effect than combinations without C. korshinskyi on P-deficient soils. Compared with monocultures, leaf [Mn] and [P] of species that are inefficient at P mobilization increased by 27 and 21% when grown with C. korshinskyi (i.e. interspecific P facilitation via carboxylates) rather than next to another inefficient P-mobilizing species. This experimental result was supported by a meta-analysis including a range of efficient P-mobilizing species. Phosphorus facilitation enhanced the relative complementarity effect in low-P environments, related to a greater change in several facilitated species of their root morphological traits relative to those in monoculture. Using leaf [Mn] as a proxy, we highlight a vital mechanism of interspecific P facilitation via belowground processes and provide evidence for the pivotal role of P facilitation mediated by the plasticity of root traits in biodiversity research.资源互补性可提升多样植物群落的生态系统功能，但促进作用对互补效应增强的贡献机制仍未得到充分阐明。本研究以叶片锰浓度([Mn])作为根际羧化物浓度的替代指标，探究磷(P)促进作用介导的植物互补新机制。盆栽试验结果表明，在缺磷土壤上，包含高效磷动员物种科尔津斯基苔草（Carex korshinskyi）的植物组合，其生物量与相对互补效应均显著高于不含该物种的组合。与单作群落相比，当与科尔津斯基苔草伴生时（即通过羧化物介导的种间磷促进作用），磷动员效率较低的物种的叶片锰浓度与磷浓度分别提升27%与21%，而当与另一磷动员低效物种邻体生长时则无此增益。涵盖多种高效磷动员物种的元分析结果进一步验证了上述实验结论。在低磷环境中，磷促进作用可增强相对互补效应，这与若干受促进物种的根系形态性状相较于单作时发生更显著的可塑性变化密切相关。本研究以叶片锰浓度为替代指标，揭示了通过地下过程实现的种间磷促进作用的关键机制，并为根系性状可塑性介导的磷促进作用在生物多样性研究中的核心地位提供了实证依据。